Table of Content

12 October 2021, Volume 47 Issue 10

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REVIEW

Research advance on optimizing annual distribution of solar and heat resources for double cropping system in the Yellow-Huaihe-Haihe Rivers plain

ZHOU Bao-Yuan, GE Jun-Zhu, SUN Xue-Fang, HAN Yu-Ling, MA Wei, DING Zai-Song, LI Cong-Feng, ZHAO Ming

Acta Agronomica Sinica. 2021, 47(10):  1843-1853.  doi:10.3724/SP.J.1006.2021.13012

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Optimizing the distribution of annual solar and heat resources is an important way to improve the annual yield and resource use efficiency without increasing input for the winter wheat-summer maize of the Yellow-Huaihe-Haihe Rivers plain. During 1980s, the researchers began to explore ways to increase the efficiency utilization of solar and heat resources from the sowing/harvest adjustment, variety selection, and intensive cropping system innovation. Based on study of matching relation between crop growth and resources, a technological approach to optimize the distribution of solar and heat resources was put forward by strengthening the high photosynthetic efficiency of “C₄ maize”. Then, the winter wheat and summer maize “double late” technology, winter wheat/spring maize/summer maize, winter wheat/spring maize/summer maize/autumn maize cropping systems were established, which realized high yield and high efficient utilization of resources. In this paper, we reviewed current theoretical and regulation approaches for optimizing distribution of solar and heat resources of double cropping system in the Yellow-Huaihe-Haihe Rivers plain. Then proposed a quantitative and optimal resources distribution method for double cropping system, and set up the unified quantitative indexes for resources distribution between winter wheat and summer maize, which could provide theory support for further increasing anniversary production and resource utilization efficiency of the Yellow-Huaihe-Haihe Rivers plain.

CROP GENETICS & BREEDING·GERMPLASM RESOURCES·MOLECULAR GENETICS

Identification of a cotton flower organ mutant 182-9 and cloning of candidate genes

YANG Qin-Li, YANG Duo-Feng, DING Lin-Yun, ZHANG Ting, ZHANG Jun, MEI Huan, HUANG Chu-Jun, GAO Yang, YE Li, GAO Meng-Tao, YAN Sun-Yi, ZHANG Tian-Zhen, HU Yan

Acta Agronomica Sinica. 2021, 47(10):  1854-1862.  doi:10.3724/SP.J.1006.2021.04208

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Cotton is an important economic crop and the main source of natural fiber in the world. The budding, flowering and bolling during cotton growth and development directly affect the yield and quality of cotton fiber that are the main economic traits of cotton. In this study, we found a flower organ mutant (named 182-9) in transgenic cottons, which displayed the floral organ petaloid feature. PCR and Southern blotting confirmed that the foreign T-DNA was integrated into the 182-9 genome with a single copy. Comparative analysis of the resequencing data revealed that the exogenic T-DNA was inserted in the 182-9 on chromosome A11: 59086840. The insertion site was further verified by PCR and southern blot. According to the gene annotation of cotton genome, there were three candidate genes of GH_A11G2251, GH_A11G2252, and GH_ A11G2253, near to the insertion site. GH_ A11G2251 encoded AP2 genes controlling the formation of sepals and petals in the ABC model of flower organs as previous report. qRT-PCR showed that there were significant differences in the expression level of GH_A11G2251 in petals, pistil and stamens of transgenic receptor W0 and mutant 182-9. Our study provided the basis for further study of molecular mechanism in cotton floral organ development.

Genetic analysis of seedling root traits and fine mapping of the QTL qLRL4 for the longest root length in rice

TIAN Biao, DING Shi-Lin, LIU Chao-Lei, RUAN Ban-Pu, JIANG Hong-Zhen, GUO Rui, DONG Guo-Jun, HU Guang-Lian, GUO Long-Biao, QIAN Qian, GAO Zhen-Yu

Acta Agronomica Sinica. 2021, 47(10):  1863-1873.  doi:10.3724/SP.J.1006.2021.02088

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In order to analyze the genetic basis of root traits at seedling stage, we performed QTL analysis of root morphology with 148 recombinant inbred lines derived from indica variety 9311 and japonica variety Nipponbare (NPB). In two repetitions, a total of 26 QTLs were detected for the longest root length, total root length, root surface area, root volume, and root diameter, distributed on chromosomes 1, 2, 4, 7, 9, 10, and 11 in rice. Four QTL clusters on chromosomes 2, 4, 7, and 10 were found, including a major QTL qLRL4 controlling the longest root length. To fine mapping of the major QTL, we constructed a near isogenic line NIL-qLRL4 with a segment from NPB between markers IND4-1 and IND4-4 with 9311 background. With a F₂ population derived from the NIL-qLRL4 and 9311, we fine mapped the qLRL4 within ~68.23 kb region between markers IND4-1 and IND4-3, where eight candidate genes located. Fine mapping of this QTL for root length will help explore genetic mechanism of root elongation and morphogenesis in rice.

QTL mapping and QTL × Environment interaction analysis of pod and seed related traits in cultivated peanut (Arachis hypogaea L.)

MENG Xin-Hao, ZHANG Jing-Nan, CUI Shun-Li, Charles Y. Chen, MU Guo-Jun, HOU Ming-Yu, YANG Xin-Lei, LIU Li-Feng

Acta Agronomica Sinica. 2021, 47(10):  1874-1890.  doi:10.3724/SP.J.1006.2021.04216

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Pod and seed traits are important agronomy traits, which are closely related to yield in cultivated peanut (Arachis hypogaea L.). In the present study, to identify molecular markers closely linked to pod and seed traits, a RIL₈ population with 315 families was developed that derived from Jihua 5 with large pod and M130 with small pod of US germplasm. A genetic linkage map containing 363 polymorphic loci was constructed using SSR, AhTE, SRAP, and TRAP markers. All polymorphic loci were mapped on 21 linkage groups, which spanned 1360.38 cM with an average distance of 3.75 cM. Subsequently, a total of 97 QTLs for pod and seed traits were identified by ICIM method at five environments from 2017 to 2018, explaining the phenotypic variations of 2.36%-12.15%, and located on A02, A05, A08, A09, B02, B03, B04, B08, and B09 chromosomes. Among them, nine QTLs were detected for pod length, 13 QTLs for pod width, 14 QTLs for pod thickness, 11 QTLs for seed length, 13 QTLs for seed width, 13 QTLs for hundred-pod weight, 10 QTLs for hundred-seed weight. Four QTLs with major effect were detected, including qPWA08.1, qPTA08.3, qPTA08.4, and qSWB08.5, which explained the phenotypic variations of 10.02%-12.15%. Furthermore, 45 stable QTLs were repeatedly detected in more than three environments. QTL clusters were detected on A02, A08, B02, B04, and B08 chromosomes, respectively. In addition, 15 epistatic QTLs were identified that explaining phenotypic variation of 10.23%-51.84%. These results will provide an important theoretical basis for molecular marker-assisted breeding of pod and seed traits in peanut.

Genome-wide association study of pre-harvest sprouting traits in wheat

XIE Lei, REN Yi, ZHANG Xin-Zhong, WANG Ji-Qing, ZHANG Zhi-Hui, SHI Shu-Bing, GENG Hong-Wei

Acta Agronomica Sinica. 2021, 47(10):  1891-1902.  doi:10.3724/SP.J.1006.2021.01078

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To understand the genetic mechanism of wheat pre-harvest sprouting (PHS) in wheat breeding, it is significant to explore marker loci and candidate genes associated with PHS resistance using intact spikes. In this study, a total of 207 wheat varieties (lines) from China and 16,686 SNP markers were analyzed in wheat whole genome. The mixed liner model (Q + K) was used to analyze PHS phenotypic data in three environments. Genome-wide association study showed that there were abundant phenotypic variations in different environments and wheat varieties (lines). The coefficient of variation was 0.34 and 0.25, the polymorphic information content of value (PIC) was from 0.01 to 0.38, and the attenuation distance of whole genome LD was 3 Mb. The population structure and principal component analysis revealed that 207 wheat varieties (lines) could be divided into three subgroups. GWAS results indicated that 34 SNP markers were detected, which were significantly associated with pre-harvest sprouting at P < 0.001. They were located on chromosomes 3A, 3B, 4A, 4B, 5D, 6A, 6B, 6D, 7B, and 7D, and each explained 5.55%-11.63% of phenotypic variation. There were 16 markers loci detected in more than two environments, and the marker Np_Ex_c14101_22,012,676 on 6B chromosome detected in E1, E2, and average environment. Meanwhile, 13 candidate genes were screened out by mining association loci with large phenotypic effect value and stable inheritance. TraesCS3A01G589400LC, TraesCS6B01G138600/TraesCS6B01G516700LC/TraesCS6B01G548900LC, TraesCS6D01G103600, and TraesCS7B01G200100 could affect seed dormancy by regulating the sensitivity of endogenous ABA in plants. The F-box proteins were encoded by TraesCS3B01G415900LC, TraesCS6A01G144700LC, and TraesCS6B01G294800, which played major roles in plant hormone signal transduction, light signal transduction, and flower organ development. TraesCS6A01G108800, TraesCS6B01G138200/ TraesCS6B01G293700 encoded Myb transcription factor family. These candidate genes are important genes related to wheat sprouting.

Fine mapping and candidate gene analysis of maize defective kernel mutant dek54

ZHOU Lian, LIU Chao-Xian, CHEN Qiu-Lan, WANG Wen-Qin, YAO Shun, ZHAO Zi-Kun, ZHU Si-Ying, HONG Xiang-De, XIONG Yu-Han, CAI Yi-Lin

Acta Agronomica Sinica. 2021, 47(10):  1903-1912.  doi:10.3724/SP.J.1006.2021.03060

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Maize kernel is closely related to yield and nutritive quality. Study on the function of maize kernel development relative genes provides important basis for the molecular mechanism analysis, yield increasing and nutritive quality improving. B73 pollen was treated with ethyl methylmethanesulfonate (EMS) and a defective maize kernel defective kernel 54 (dek54) was screened. dek54 had small mature kernel, wrinkled and whitened seed coat phenotype. Genetic analysis indicated that dek54 is a recessive mutant controlled by a single gene. Paraffin sections showed starchy endosperm cells of dek54 had irregular shape and dense arrangement at developmental stage. Scanning electron microscopy observation indicated that protein bodies around starch granules in the central region of the dek54 mature kernel endosperm were fewer and arranged more loosely compare to wild type. Total protein, zein, amino acids components contents and total nitrogen content of dek54 mature kernel were significantly lowered compared with the wild type. dek54 was located on chromosome 7 within the interval of the physical distance of about 290 kb between markers SSR6 and SSR7. Sequencing revealed that the 351th base G on the 2nd exon of Zm00001d019294 gene changed into A, which led to the premature termination of the protein translation. Zm00001d019294 gene was specifically expressed in immature maize kernel, and has the highest expression in 12 DAP (days after pollination) immature kernel. Targeted mutation was performed using CRISPR/Cas9 system to identify that mutant phenotype was caused by candidate gene Zm00001d019294. Dek54 encoded an MFS (major facilitator superfamily) protein and had high homology with ZmNRT1.5 (nitrate transporter). Besides, Dek54 protein was localized in the plasma membrane of maize protoplasts. The study of dek54 laid the foundation for the molecular mechanism analysis of maize kernel development.

Identification and analysis of sHSP gene family in Gossypioides kirkii

FAN Kai, PAN Xin-Feng, MAO Zhi-Jun, YE Fang-Ting, LI Zhao-Wei, LIN Wei-Wei, LIN Wen-Xiong

Acta Agronomica Sinica. 2021, 47(10):  1913-1926.  doi:10.3724/SP.J.1006.2021.04235

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Small heat shock protein (sHSP) has the lowest molecular weight in heat shock protein and sHSP has the highly conserved α-crystallin domain. The sHSP family is very important in response to various stresses, but the identification and analysis of sHSP gene family in Gossypioides kirkii have not been reported. In this study, we identified 39 GksHSPs with 10 subfamilies in Gossypioides kirkii. There were seven gene duplication events in GksHSP family and all of duplicated gene pairs were involved in segmental duplication events. The cotton-specific whole genome duplication event primarily resulted in the GksHSP expansion. The GksHSP expansion was also related to the protein kinase, mitochondrial carrier protein, and auxin responsive protein. Besides, GksHSP members might respond to various stresses by ABA/MeJA-mediated pathways, and GksHSP26 and its corresponding orthologous genes in Gossypium hirsutum were very important in stress responses. These results could provide the theoretical basis of the breeding of stress tolerance in Gossypioides kirkii and cotton.

Effects on drought tolerance by pladienolide B and rice with high expression of C₄-PEPC

SONG Ni-Xi, LI Xia, WANG Jin, WU Bo-Han, CAO Yue, YANG Jie, XIE Yin-Feng

Acta Agronomica Sinica. 2021, 47(10):  1927-1940.  doi:10.3724/SP.J.1006.2021.03064

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To investigate the intrinsic mechanism of alternative splicing (AS) participated in drought tolerance in plants, the effects of macrolides pladienolide B (PB, one of the AS inhibitors) were studied using the phosphoenolpyruvate carboxylase (C₄-PEPC) rice (PC) and “Kitaake” (WT) rice lines in pot experiments and hydroponics experiments, respectively. The changes of photosynthetic parameters, total soluble sugar and sugar components contents, some main antioxidant enzyme activities and antioxidant contents, Ca²⁺, NO, H₂O₂, ABA contents, transcript levels of sucrose nonfermenting-1 (SNF1)-related protein kinases (SnRKs), arginine/serine-rich proteins (SR proteins), and PEPC both in C₄ and C₃ type of the functional leaves in rice lines were measured. Agronomic traits of the WT and PC were recorded in the mature period. In pot experiment, compared with the natural drought treatment alone, the treatment of 0.5 µmol L^-1 PB with drought at booting stage had a significant decline on agronomic traits of the tested rice. Among them, plant height, panicle number per plant, filled grain number per panicle, and grain yield per plant in PC were significantly higher than those of WT. In the hydroponics experiment with 0.5 µmol L ^-1 PB combined with 10% mmol L^-1 polyethylene glycol 6000 (PEG-6000) to simulate drought stress, compared with PEG treatment, net photosynthetic rate, relative water content, total soluble sugar content, proline content, SOD activity, POD activity, CAT activity, and PEPC activity were significantly increased in PC than those of WT. Similarly, the contents of sucrose, glucose, fructose, and Ca²⁺ of leaves in PC lines were significantly higher than those of WT. It was noteworthy that the relative gene expression levels of C₄-PEPE, Osppc2a, SnRK2s (SAPK8 and SAPK9), SnRK1s (OsK1a, OsK24, and OsK35), and SR proteins (SR33, SR40, RS29, RS2Z21, and RS2Z38) under PEG+PB treatment were significantly lower than those under PEG treatment. It was further verified by using 10 mmol L^-1 EGTA experiments [Ethylene glycolbis (aminoethylether)-tetra-acetic acid, a chelate solution of calcium ions] that Ca²⁺ were involved in the drought response by regulating the transcript levels of SR proteins genes in rice. In addition, the Ca²⁺ content in PC lines was significantly correlated with soluble protein content, ABA content, and RS33 transcript level, respectively. In conclusion, AS participated in drought response by regulating the expression of SR related genes through sugar signal both SnRK1s and SnRK2s, and calcium ion as well, which played a positive role in drought tolerance in rice. Compared with WT, PC had a stronger positive effect, which was closely related to its high endogenous Ca ²⁺ content and the contents of sucrose, glucose, fructose.

Molecular cloning, expression, and enzyme kinetic analysis of a phenylalanine ammonia-lyase gene in Pinellia ternate

HE Xiao, LIU Xing, XIN Zheng-Qi, XIE Hai-Yan, XIN Yu-Feng, WU Neng-Biao

Acta Agronomica Sinica. 2021, 47(10):  1941-1952.  doi:10.3724/SP.J.1006.2021.04227

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In this study, based on the transcriptome data, a phenylalanine ammonia lyase gene was cloned and named PtPAL using Pinellia ternate as the experimental material. The analysis of sequence structure and systematic evolution revealed that the length of the gene was 2289 bp, encoding 762 amino acids, and the termination codon was TAA. PtPAL was the similarity of 78% compared with monocot Lilium regale PAL, with PAL-HAL, PLN02457, phe_am_lyase, Lyase_aromatic, and HutH domains that belonging to the Lyase_I_like superfamily. Phylogenetic tree analysis showed that PtPAL was closely related to the monocotyledon Lilium regale, Ananas comosusm, and Elaeis guineensis, and thus belonging to Moncotyledons. Real-time fluorescent qPCR indicated that the relative expression level of PtPAL gene was the highest in leaves, followed by tubers and roots, and the lowest in flowers. The functional expression analysis of PtPAL gene revealed that the PtPAL recombinant protein could efficiently catalyze L-Phe to t-CA, and the optimal pH and temperature of the reaction were 9.0℃ and 70℃, respectively. K_m, V_max, K_cat, and K_cat/K_m of PtPAL were 0.89 mmol L ^-1, 63.96 nKat mg^-1, 6.56 s^-1, and 7.37×10³ s^-1 M^-1. Further exploration of the effect of metal ions on PtPAL enzyme activity showed that Ba²⁺ could significantly enhance PtPAL enzyme activity, and Mn²⁺, Co²⁺, Cu²⁺, and Zn²⁺ inhibit the activity of PtPAL enzyme. This study lays the foundation for further research of the functional characteristics of PtPAL and the metabolic pathways of amphetamine alkaloids in Pinellia ternata.

TILLAGE & CULTIVATION·PHYSIOLOGY & BIOCHEMISTRY

Characteristics and differences of rice yield, quality, and economic benefits under different modes of comprehensive planting-breeding in paddy fields

CHE Yang, CHENG Shuang, TIAN Jin-Yu, TAO Yu, LIU Qiou-Yuan, XING Zhi-Peng, DOU Zhi, XU Qiang, HU Ya-Jie, GUO Bao-Wei, WEI Hai-Yan, GAO Hui, ZHANG Hong-Cheng

Acta Agronomica Sinica. 2021, 47(10):  1953-1965.  doi:10.3724/SP.J.1006.2021.02068

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To explore the characteristics and differences in yield, photosynthetic matter production, quality and economic benefits of rice under different modes of comprehensive planting-breeding in paddy fields, six modes including rice crayfish (RC), rice turtle (RT), rice loach (RL), rice catfish (RF), rice koi (RK), and rice duck (RD) were arranged using Nanjing 9108 (a high-quality rice variety) as the experimental material in 2018 and 2019. Comparing these modes with rice cultivation under rice-wheat rotation (CK), the effects of different modes of comprehensive planting-breeding in paddy fields on quality, yield and yield component of rice, characteristics of photosynthetic matter production, and economic benefits were systematically investigated in this study. The results showed that, compared with CK, the rice yield of different modes of comprehensive planting-breeding in paddy fields was significantly decreased by 3.66%-7.54%, and the RD mode reduced the least, and the RK mode reduced the most. Compared with CK, the reduction of rice yield in different modes of comprehensive planting-breeding in paddy fields was mainly due to lower dry matter accumulation at maturity stage, which was resulted from the smaller leaf area index, lower photosynthetic potential, crop growth rate, and net assimilation rate in main growth stages; and due to less total number of spikelets, which was caused by significant decreasing in panicle number per hectare and number of spikelets per panicle. Compared with CK, the different modes of comprehensive planting-breeding in paddy fields significantly reduced the head milled rice rate by 2.40%-4.37%, decreased the chalkiness by 8.14%-11.14%, increased the amylose content by 9.35%-13.80%, reduced the protein content by 6.29%-10.01%, and raised the taste value by 3.91%-11.69%. Compared with CK, the peak viscosity, hot viscosity, final viscosity, and breakdown of RVA parameters of rice starch were increased by 2.75%-12.65%, 3.24%-19.63%, 2.47%-14.79%, and 1.67%-5.78%, respectively, while the setback was decreased by 2.54%-15.15%. The economic benefits of different modes of comprehensive planting-breeding in paddy fields were 80.93%-511.52% higher than CK, which was mainly due to the increase in the income of aquatic (poultry) breeding products and the increase in the price of rice quality. In conclusion, comprehensive planting-breeding in paddy fields was an alternative rice planting mode, that could guarantee a stable rice yield, improve rice quality, and increase the comprehensive benefits.

Effects of combined application of slow release nitrogen fertilizer and urea on carbon and nitrogen accumulation in mechanical transplanted hybrid rice

LYU Teng-Fei, SHEN Jie, DAI Zou, MA Peng, YANG Zhi-Yuan, ZHENG Chuan-Gang, MA Jun

Acta Agronomica Sinica. 2021, 47(10):  1966-1977.  doi:10.3724/SP.J.1006.2021.02059

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To explore the effects of combined application of slow release nitrogen fertilizer and urea on carbon and nitrogen accumulation of machine-transplanted indica hybrid rice in southwestern China. A split-plot design experiments were carried out in 2016 and 2017 repeatedly, with two machine-transplanting methods as main plot, and four nitrogen treatments as subplot using F you 498 as the experimental variety. The contents of carbon (C) and nitrogen (N), and their related key enzyme activities were investigated. Results showed that, compared with the blanket-seedling rice, potted-seedling increased key enzyme activities of C and N metabolism of young panicles and flag leaves, C and N accumulation at heading and maturity stage, C accumulation and C/N at jointing stage, C/N of panicle at heading and maturity stage, resulting in the yield improvement of F you 498. Compared with 100% slow release N fertilizer (SRNF) as base, 70% SRNF as base + 30% urea as panicle (SBUP) significantly improved key enzyme activities of C and N metabolism, C/N at jointing stage, C accumulation at heading and maturity stage, leading to a further yield growth in machine-transplanting method. Meanwhile, this study suggested that C/N of the high-yield groups of machine-transplanting hybrid rice should be controlled 1.85-2.12, 2.47-2.82, and 3.34-3.53 at jointing, heading and maturity stages, respectively.

Competitive effect of soybean density on yield formation in maize/soybean intercropping systems

REN Yuan-Yuan, ZHANG Li, YU Yao-Chuang, ZHANG Yan-Jun, ZHANG Sui-Qi

Acta Agronomica Sinica. 2021, 47(10):  1978-1987.  doi:10.3724/SP.J.1006.2021.04226

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Crop intercropping system in arid areas is an important planting method for optimizing crop population quality and improving crop yield. There are few reports on the mechanism of crop intercropping competitive advantage in terms of yield components. In this study, to explore the mechanism of crop competition for increasing the yield of intercropping systems, three soybean densities and four row proportions (maize and soybean intercropping with 2:0, 0:2, 2:2, and 2:4) were used to investigate the changes of competition index, yield components, and yield of intercropping system. The results showed that the yield of intercropping system with different row proportion and soybean density was increased by 14%-23%. The actual yield loss of maize was greater than 0, the actual yield loss of soybean was less than 0. The ear weight, ear length, ear diameter, grain weight per ear, cob weight, and 1000-grain weight of maize in intercropping systems were significantly higher than those in monoculture. Except pod length and internode length of main stem, the grain weight per plant, pod number per plants, grain number per plant, effective grain number per plants, nodes on main stem, and 100-grain weight of soybean in intercropping systems were lower than that of monoculture. And there was no significant difference between intercropping and monoculture. The competition ratio of maize was greater than one, and the competition ratio of soybean was less than one. The competition ratio of maize and soybean was 2.08, 1.84, 1.68 and 0.49, 0.56, 0.63, respectively, with three soybean densities, indicating that with the increase of soybean density competition ratio of maize increased while competition ratio of soybean decreased in intercrops. The aggressivity of maize was positive value, and that of soybean was less than zero in intercropping system. Maize yield was positively correlated with cob weight, 1000-grain weight, ear weight, grain weight per ear, ear length, and row kernel number negatively correlated with barren tip length. Path analysis revealed that in the direct effect, grain weight per ear contributed the most to maize yield (2.18); in indirect effect, cob weight and 1000-grain weight contributed more to maize yield 1000-grain weight per ear (1.64 and 1.58). In conclusion, maize intercropped with soybean had intercropping advantages that derived from grain weight per ear.

Effects of uniconazole on physiological characteristics and microstructure under waterlogging stress at seedling stage in soybean

WANG Shi-Ya, ZHENG Dian-Feng, FENG Nai-Jie, LIANG Xi-Long, XIANG Hong-Tao, FENG Sheng-Jie, JIN Dan, LIU Mei-Ling, MU Bao-Min

Acta Agronomica Sinica. 2021, 47(10):  1988-2000.  doi:10.3724/SP.J.1006.2021.04233

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To explore the effects of waterlogging stress on the physiological characteristics and microstructure of soybean and the mitigation effect of S₃₃₀₇, the physiological characteristics of soybean leaves and roots, the microstructure of hypocotyls and the regulation effect of S₃₃₀₇ were investigated using Kenfeng 14 as the experimental material with S₃₃₀₇ sprayed on the leaves of soybean at V1 stage and five days after waterlogging stress in a pot experiment. The results showed that waterlogging stress increased the number of ventilated tissues in soybean hypocotyl, and the area of ventilated tissues increased gradually with the prolongation of waterlogging stress. S₃₃₀₇ could improve soybean adaptability to waterlogging adversity, increase the number of ventilated tissue and cope with the hypoxia stress by waterlogging stress on plants. Compared with CK, waterlogging stress increased the accumulation of ROS and membrane lipid peroxidation in leaves and roots, and gradually increased with the prolongation of stress time. Meanwhile, the activity of enzymatic antioxidant defense system was enhanced at early stage under waterlogging stress, resulting in an increase in the content of osmotic regulatory substances, which decreased with the prolongation of stress time. S₃₃₀₇ can promote the activity of antioxidant enzyme in leaves and roots, inhibit the excessive accumulation of ROS and MDA content, maintain a high content of osmotic regulation substances, and alleviate the damage caused by waterlogging stress. In summary, there were differences in response to different organs under waterlogging stress. S₃₃₀₇ can alleviate the damage to soybean plants caused by waterlogging stress to a certain extent.

Effects of exogenous 2,4-Epibrassinolide on nitrogen metabolism and TAs metabolism of Atropa belladonna L. under NaCl stress

XIN Zheng-Qi, DAI Huan-Huan, XIN Yu-Feng, HE Xiao, XIE Hai-Yan, WU Neng-Biao

Acta Agronomica Sinica. 2021, 47(10):  2001-2011.  doi:10.3724/SP.J.1006.2021.04238

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To explore the physiological mechanism of exogenous 2,4-Epibrassinolide (EBR) regulating NaCl tolerance of A. belladonna, potted A. belladonna seedlings was used as the experimental materials, and exogenous EBR was applied to A. belladonna seedlings with the different concentrations (0.05, 0.1, 0.2, and 0.4 mg L^-1) of exogenous EBR and different treatment times (5, 10, 15, and 20 days) on the nitrogen metabolism, the contents of the secondary metabolites and precursor substances in the synthesis pathway of TAs, and the relative expression levels of key enzyme genes. NaCl stress caused inhibitory effect on nitrogen metabolism in A. belladonna, however the content of nitrate nitrogen increased significantly, the content of ammonium nitrogen decreased, the content of free amino acids, soluble protein, and the activity of key enzymes of nitrogen metabolism increased to some extent under exogenous EBR treatment, which indicating the exogenous EBR could effectively enhance the nitrogen metabolism capacity. NaCl stress was not conducive to the synthesis and accumulation of alkaloids. The synthesis of precursor substances and the relative expression levels of key enzyme genes in TAs pathway significantly were reduced under NaCl stress. The contents of ornithine, arginine, polyamine, and the activities of key enzymes in putrescine synthesis were increased with the exogenous EBR of 0.1 mg L^-1. Moreover, exogenous EBR could effectively enhance the contents of hyoscyamine and scopolamine by increasing the relative expression levels of key enzyme genes TR I and H6H in TAs pathway. In conclusion, the appropriate concentration of exogenous EBR could effectively relieve the damage of NaCl stress to the physiological metabolism in A. belladonna, and the exogenous EBR could improve NaCl tolerance of belladonna seedlings by increasing nitrogen metabolism and promoting the production and accumulation of TAs.

Effects of sowing date on the numbers of branches and spikelets per panicle of machine-transplanted indica hybrid rice at different tiller positions

ZHONG Xiao-Yuan, DENG Fei, CHEN Duo, TIAN Qing-Lan, ZHAO Min, WANG Li, TAO You-Feng, REN Wan-Jun

Acta Agronomica Sinica. 2021, 47(10):  2012-2027.  doi:10.3724/SP.J.1006.2021.02074

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In order to explore the effects of sowing date on the numbers of branches and spikelets per panicle of machine-transplanted indica hybrid rice on the main stems (MS), primary tillers (PT) and secondary tillers (ST), a split plot field experiment was conducted with five sowing dates by using two indica hybrid rice varieties (F you 498 and Yixiangyou 2115) as materials. The results were as follows: (1) The numbers of spikelets on the primary branches and secondary branches, and the numbers of secondary branches on different tiller positions ranked: MS>PT>ST; the numbers of spikelets on the primary branches and secondary branches, and the numbers of secondary branches on the MS and PT, as well as the whole hill, were increased with delaying sowing date. These contributed to the increase in the numbers of total branches and spikelets per panicle on the MS, PT, and averaged over all panicles in a hill with delaying sowing date. (2) The correlation analysis showed that the numbers of total branches and spikelets per panicle on the MS, PT, and ST were significantly positively correlated with the numbers of total branches and spikelets averaged over all panicles in a hill, and the correlation coefficients ranked: MS>PT>ST. Compared to the ST, the numbers of total branches and spikelets of the MS and PT possessed higher contributions to the numbers of total branches and spikelets averaged over all panicles in a hill. (3) The branches and spikelets traits on the MS, PT, and the averaged over all panicles in a hill of different panicle types were significantly affected by the temperature and sunshine duration at panicle differentiation stage. Most branches and spikelets traits on the MS, PT, and the mean per panicle per hill were significantly positively correlated with the average daily maximum and mean temperatures, and average daily sunshine hours. In conclusion, the numbers of branches and spikelets on the MS, PT, and ST were differed to sowing date, and the using of varieties with large panicle type was helpful to increase the numbers of branches and spikelets of machine-transplanted indica hybrid rice. Furthermore, on the basis of ensuring high numbers of primary tillers, the increase in the numbers of branches and spikelets per panicle was crucial for the early sowing treatment to increase the grain yield of machine-transplanted indica hybrid rice, while the later-sowing treatment could increase the seed-setting rate and grain weight with higher number of spikelets per panicle.

Model for monitoring leaf dry weight of double cropping rice based on crop growth monitoring and diagnosis apparatus

LI Yan-Da, CAO Zhong-Sheng, SHU Shi-Fu, SUN Bin-Feng, YE Chun, HUANG Jun-Bao, ZHU Yan, TIAN Yong-Chao

Acta Agronomica Sinica. 2021, 47(10):  2028-2035.  doi:10.3724/SP.J.1006.2021.02077

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The quantitative, convenient and non-destructive monitoring of leaf dry weight (LDW) is critical for precise management in double cropping rice production. The objective of this study is to verify the accuracy of crop growth monitoring and diagnosis apparatus (CGMD, a passive multi-spectral sensor containing 810 nm and 720 nm wavelengths) in monitoring growth index of double cropping rice, and establish the model for monitoring LDW of double cropping rice based on CGMD. Plot experiments were conducted in Jiangxi province in 2016 and 2017, including eight early and late rice cultivars and four nitrogen application rates. The normalized difference vegetation index (NDVI), differential vegetation index (DVI), and ratio vegetation index (RVI) were measured at tillering, jointing, booting, heading and filling stages with two spectrometers, CGMD and analytical spectral devices field-spec handheld 2 (ASD FH2, a passive hyper-spectral sensor containing 325 nm to 1075 nm wavelengths). In order to verify the measurement precision of CGMD, the correlation relationship of vegetation indices between CGMD and ASD FH2 was analyzed. The LDW monitoring models of double cropping rice were established based on CGMD from an experimental dataset and then validated using an independent dataset involving different early and late rice cultivars and nitrogen application rates. The results indicated that the LDW of early and late rice were increased with the increase of nitrogen application rate at different growth stages, and exhibited “low-high-low” dynamic variation trend with early and late rice development progress. The NDVI, DVI, and RVI from CGMD and ASD FH2 were significantly correlation. The correlation coefficient (r) of NDVI, DVI, and RVI from CGMD and ASD FH2 were 0.9535-0.9972, 0.9099-0.9948, and 0.9298-0.9926, respectively. This result indicated that there was highly consistent of vegetation indices from CGMD and ASD FH2, and the CGMD could replace expensive ASD FH2 to measure NDVI, DVI and RVI. Compared with the three vegetation indices based on CGMD, the correlation between RVI_CGMD and LDW was the highest. The power function model based on RVI_CGMD could accurate monitoring LDW with a determination coefficient (R²) in the range of 0.8604-0.9216, the root mean square error (RMSE), relative root mean square error (RRMSE), and r of model validation in the range of 12.97-17.87 g m^-2, 4.88%-16.79%, and 0.9951-0.9992, respectively. Compared with the manual sampling measure LDW, CGMD method can timely and accurately measure the LDW dynamic variation of double cropping rice, which had a potential to be widely applied for growth precision diagnosis and high yield and high efficiency cultivation in double cropping rice production.

RESEARCH NOTES

Combining QTL-seq and linkage analysis to identify the QTL of mesocotyl elongation in rice (Oryza sativa L.)

LIU Chang, MENG Yun, LIU Jin-Dong, WANG Ya-Mei, Guoyou Ye

Acta Agronomica Sinica. 2021, 47(10):  2036-2044.  doi:10.3724/SP.J.1006.2021.02082

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Mesocotyl length is an important trait, which affects seedling establishment and early seedling vigor after dry direct seeding. Identifying the loci related to mesocotyl elongation, analyzing the genetic mechanism and selecting varieties with long mesocotyl is the most economic and effective way to promote the popularization of dry direct seeding technology. In this study, an F₂ population constructed with ‘Changai’ (an extremely long mesocotyl variety) and ‘IR 145’ (an extremely short mesocotyl variety) was used to construct long and short DNA pool, which were re-sequenced at 50×level. Two methods, ΔSNP-index and G-value, were used to identify the quantitative trait loci (QTL) for mesocotyl elongation. A QTL named as qML3, located in the region of 29.56-33.28 Mb on chromosome 3 were detected. After linkage analysis of 184 F₂ lines with the newly developed KASP markers based on this locus, the region was narrowed down to 28.89-31.03 Mb. Combining the results of gene annotation, linkage analysis, and gene expression analysis, LOC_Os03g52450, LOC_Os03g56060, LOC_Os03g58290, LOC_Os03g58300, LOC_Os03g58320, LOC_Os03g56050, and LOC_Os03g57640 were speculated to be candidate genes in this region. These genes were involved in the regulation of plant hormones as well as the mechanism of cell division. This study uncovers a locus related to rice mesocotyl elongation and is helpful for the breeding of long mesocotyl varieties.

Cloning and functional identification of gene OsATS in rice

LI Xiao-Xu, WANG Rui, ZHANG Li-Xia, SONG Ya-Meng, TIAN Xiao-Nan, GE Rong-Chao

Acta Agronomica Sinica. 2021, 47(10):  2045-2052.  doi:10.3724/SP.J.1006.2021.02079

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The plant embryo specific protein ATS3 is closely related to osmotic stress response in plants. Here, the stress resistance related gene OsATS was preliminarily studied in rice. Fluorescence quantitative PCR showed that the relative expression level of OsATS increased significantly after salt stress in rice. The overexpression vector of OsATS was constructed and transformed into Arabidopsis thaliana. The stress resistance test revealed that the overexpression of OsATS gene could significantly improve the salt tolerance of Arabidopsis thaliana at germination and adult stages. After that, the overexpression vector p1300-35s:OSATS and RNA interference vector pTCK303-OsATS-RNAi were transferred into rice. The stress tolerance analysis indicated that the salt tolerance of OsATS overexpression rice lines significantly increased at germination stage and seedling stage, while the salt tolerance of OsATS RNAi rice lines significantly decreased. Results of qRT-PCR and physiological index detection demonstrated that the relative expression levels of OSATS gene might regulate the protein content of proline and LEA cells by regulating the expression of OsP5CS1, OsLEA3-1 and OsPDH, thus affecting the salt tolerance in rice. This study preliminarily revealed the stress resistance function of OSATS gene, which laid a foundation for improving rice stress resistance by adjusting the relative expression level of OSATS gene.

Evaluation of resistance to stripe rust and molecular detection of resistance genes of 93 wheat landraces from the Qinghai-Tibet spring and winter wheat zones

ZHAO Xu-Yang, YAO Fang-Jie, LONG Li, WANG Yu-Qi, KANG Hou-Yang, JIANG Yun-Feng, LI Wei, DENG Mei, LI Hao, CHEN Guo-Yue

Acta Agronomica Sinica. 2021, 47(10):  2053-2063.  doi:10.3724/SP.J.1006.2021.01073

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Wheat stripe rust (yellow rust), caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most serious diseases in wheat. To address the threat of predominant Pst races to wheat production and screen resistance resources to breed new wheat cultivars in China, the resistance of 93 wheat landraces derived from Qinghai-Tibet spring and winter wheat zones to stripe rust were evaluated at seedling stage and adult plant stage, and the Yr genes that they might carry were detected. The resistance of 93 wheat landraces were evaluated at seedling stage in a greenhouse with two Pst races CYR32 and CYR34, and at adult plant stage under four field conditions with the mixture of Pst races (CYR32, CYR33, CYR34, Su11-4, Su11-5, and G22-14) in Chongzhou and Mianyang, Sichuan during 2015-2016, 2017-2018, and 2018-2019 cropping seasons, respectively. The panel of wheat landraces was detected with flanking markers closely linked to stripe rust resistance genes Yr5, Yr10, Yr18, Yr24 (=Yr26), Yr48, Yr65, and Yr67. Resistance evaluation indicated that four landraces (4.30%) were resistant to CYR32, three (3.26%) resistant to CYR34, and one was resistant to both CYR32 and CYR34 at seedling stage. Ten landraces displayed resistance to mixed races at adult plant stage under four field conditions. Molecular detection indicated that 11, 40, and 1 landrace might carry Yr18, Yr48, and Yr65, respectively. Seven landraces may carry both Yr18 and Yr48. In addition, no Yr genes were detected in the three resistant wheat landraces, indicating that these wheat landraces might carry other known or unknown stripe rust resistance genes. The wheat landraces derived from Qinghai-Tibet spring and winter wheat zones showed low levels of resistance to the current predominant Pst races in China, and they carried less resistance genes. These wheat landraces with good resistance and carrying known or unknown resistance genes should be valued to explore novel stripe rust resistance genes and accelerate their utilization in wheat breeding program.